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PubMed1981

Hypoglycemic brain injury: metabolic and structural findings in rat cerebellar cortex during profound insulin-induced hypoglycemia and in the recovery period following glucose administration.

Previous results have shown that severe, prolonged hypoglycemia leads to neuronal cell damage in, among other structures, the cerebral cortex and the hippocampus but not the cerebellum. In order to study whether or not this sparing of cerebellar cells is due to preservation of cerebellar energy stores, hypoglycemia of sufficient severity to abolish spontaneous EEG activity was induced for 30 and 60 min. At the end of these periods of hypoglycemia, as well as after a 30 min recovery period, cerebellar tissue was sampled for biochemical analyses or for histopathological analyses or for histopathological analyses by means of light and electron microscopy. After 30 min of hypoglycemia. the cerebellar energy state, defined in terms of the phosphocreatine, ATP, ADP, and AMP concentrations, was better preserved than in the cerebral cortex. After 60 min, gross deterioration of cerebellar energy state was observed in the majority of animals, and analyses of carbohydrate metabolites and amino acids demonstrated extensive consumption of endogenous substrates. In spite of this metabolic disturbance, histopathologic alterations were surprisingly discrete. After 30 min, no clear structural changes were observed. After 60 min, only small neurons in the molecular layer (basket cells) were affected, while Purkinje cells and granule cells showed few signs of damage. The results support our previous conclusion that the pathogenesis of cell damage in hypoglycemia is different from that in hypoxia-ischemia and indicate that other mechanisms than energy failure must contribute to neuronal cell damage in the brain.

Adenosine Diphosphate↗
PubMed1990

Subcellular localization of a putative kainate receptor in Bergmann glial cells using a monoclonal antibody in the chick and fish cerebellar cortex.

A monoclonal antibody, IX-50, that was raised against a kainate binding protein (Mr = 49,000) from chicken cerebellum, was used in light and electron microscopic immunocytochemical studies to localize putative kainate receptors. Pre- and postembedding immunoperoxidase and immunogold methods were used in the cerebellar cortices of one to 26-day old chickens and adult rainbow trout. Immunoreactivity was detected only in association with Golgi epithelial/Bergmann glial cells. Intracellular immunoreactivity was present in the granular and agranular endoplasmic reticulum, Golgi apparatus and in lysosomes, representing the sites of synthesis, glycosylation and degradation of the protein. In the fish the granular endoplasmic reticulum was not immunoreactive. Extracellular immunoreactivity was associated with the plasma membrane. In the fish it was established that the epitope is on the outer surface of the membrane. The protein seems to be uniformly distributed along the membrane including the somata, the radial stem processes and the leafy lamellae surrounding Purkinje cell dendrites. Areas of the glial membrane in contact with other glial cells were also immunopositive. High-resolution light microscopy demonstrated all the Bergmann glial plasma membrane in the cortex, providing a "negative" image of Purkinje cell dendrites. It is apparent that Bergmann glial processes selectively outline the dendrites of the Purkinje cells by surrounding the parallel fibre terminal/Purkinje cell spine synaptic complexes. The parallel fiber terminals were highly immunoreactive for glutamate, as shown by an immunogold procedure. The association of Bergmann glial processes, carrying the Mr = 49,000 kainate binding protein, with the Purkinje cell dendrites and spine synapses could provide a basis for neuronal signalling to the Bergmann glia, possibly by glutamate.

Animals↗
PubMed1989

Multiple Purkinje Cell Recording in Rodent Cerebellar Cortex.

The spatial and temporal organization of climbing fibre activation of Purkinje cells, the so-called complex spikes, were studied in the rat cerebellar Crus II folium utilizing a multiple microeletrode recording technique. As many as 32 Purkinje cells could be simultaneously recorded by using a custom-built electronic amplifier system and a special data storage device. Analysis of the auto-correlation activity of complex spikes in any given group of Purkinje cells indicated that activation occurs with a particular rhythmicity having a base firing of 10 Hz. Cross-correlation of spontaneous complex spikes demonstrated, in addition to a particular rhythmicity, an extraordinarily high degree of synchronicity within a particular spatial distribution of Purkinje cells. Thus, Purkinje cells organized in rostro-caudal rows tend to fire within 1 ms of each other for distances as far as 800 microm (the width of a folium) from the 'master' neuron. By contrast, Purkinje cells located medial or lateral to the master neuron showed almost no cross-correlation. Administration of harmaline to the animal increased the degree of auto- and cross-correlation but did not change the spatial order of the distribution of the cross-correlation. The results indicate that the olivo-cerebellar system is organized in such a way that climbing fibre afferents may be activated in a close-to-synchronous and rhythmic fashion. The spatial distribution of these afferents over the cortex is such as to activate rostro-caudal bands of Purkinje cells which tend to fire in a close-to-synchronous manner.

Journal Article↗
PubMed1989

Tau-reactive neurofibrillary tangles in cerebellar cortex from patients with Alzheimer's disease.

In 4 cases of Alzheimer's disease (AD) a tau antiserum immunostained thin, round or flame-shaped profiles disposed around the nuclei of the cerebellar fusiform-type Golgi cells. In adjacent sections either a Bodian silver method or Congo red failed to reveal any abnormal structures. Since normal tau immunoreactivity is located on axons and is absent in formalin-fixed tissue, the tau-reactive profiles are likely to correspond to small masses of abnormal filaments, antigenically similar to those composing neurofibrillary tangles (NFT). This observation indicates that in AD the NFT formation is more diffuse than that showed with conventional histological methods.

Aged↗
PubMed2000

Constitutive expression of the 25-kDa heat shock protein Hsp25 reveals novel parasagittal bands of purkinje cells in the adult mouse cerebellar cortex.

Despite the reported absence of the 25-kDa heat shock protein Hsp25 in the rodent cerebellum, we have determined that Hsp25 is constitutively expressed in a subset of Purkinje cells in the adult cerebellum of the mouse. No other cerebellar neurons are Hsp25 immunoreactive, but there is weak staining associated with blood vessels. In the vermis, Hsp25-immunoreactive Purkinje cells are confined to two regions: one in lobules VI/VII, the other in lobules IX/X. In each region, only a subset of the Purkinje cells is immunoreactive. These cells are grouped in five parasagittal bands arranged symmetrically about the midline. The boundaries of these expression domains correspond to transverse zones previously inferred from other expression patterns. A third Hsp25-immunopositive domain is seen in the paraflocculus and flocculus. Again, only a subset of Purkinje cells within the paraflocculus and flocculus express Hsp25, revealing three distinct bands. Previous descriptions of compartmentation antigens have not differentiated between adult populations of Purkinje cells in these regions, suggesting that Hsp25 is a novel compartmentation antigen in the adult cerebellum.

Animals↗
PubMed1998

Monoclonal antibodies reveal expression of the CGRP receptor in Purkinje cells, interneurons and astrocytes of rat cerebellar cortex.

The molecular layer of adult rat cerebellum displays high levels of calcitonin gene-related peptide (CGRP) receptors, but the cellular location of the receptor remains unidentified. In an attempt to reveal the expression sites of these receptors, monoclonal antibodies raised against purified CGRP receptors from porcine cerebellar membranes were used in double-immunofluorescence experiments combined with confocal microscopy. PEP-19, a marker that is highly enriched in Purkinje cells (Pc), revealed that CGRP receptors are located in Pc cytoplasm and dendrites, where they label small puncta sometimes arranged in a row along the course of the dendrite itself. CGRP receptors were also located in inhibitory interneurons. Furthermore, as shown by double-labeling experiments with GFAP, CGRP receptor-IR labeled Golgi epithelial cells and their radial fibers (Bergmann fibers), as well as astrocytic processes encircling Pc somata. The simultaneous presence of CGRP receptors in Purkinje cells and in the glial cells that heavily enshroud Purkinje cells allows us to hypothesize that these receptors may be involved in neuron-glia interactions influencing neuronal activity.

Adrenomedullin↗
PubMed2004

Distinct glutamate receptors govern differential levels of nitric oxide production in a layer-specific manner in the rat cerebellar cortex.

To evaluate roles of nitric oxide (NO) in neural functions, it is critical to know how neural inputs activate neuronal NO synthase in individual sites. Although NMDA receptor-dependent mechanism well explains postsynaptic, robust NO production, this sole mechanism does not explain some aspects of NO production in the brain, such as the low-level production of NO and the mechanism for presynaptic NO production. We hypothesized that the glutamate receptor involved in NO production is site-specific and controls the initial NO concentration in each site. We visualized NO production mediated by NMDA, AMPA and type-1 metabotropic glutamate (mGlu-1) receptors in rat cerebellar slices and granule cells in culture, with an NO-specific fluorescent indicator, diaminofluorescein-2. AMPA receptor, but not NMDA or mGlu-1 receptor, was responsible for NO production at parallel fiber terminals, which was blocked by CNQX, tetrodotoxin or voltage-dependent calcium channel blockers. More numbers of electrical stimulation were required for NO production in the molecular layer than in other layers, suggesting that AMPA receptor activation generates NO at lower concentrations through a remote interaction with NO synthase. Although Purkinje cell does not express NO synthase, we detected NO production in Purkinje cell layer following electrical stimulation in the white matter at 50 Hz, but not at 10 Hz. This NO production was tetrodotoxin-sensitive, suggesting occurrence in the basket cell terminals, and required synergistic activation of mGlu-1 and NMDA receptors. In the granule cell layer, activation of AMPA or mGlu-1 receptor produced NO uniformly, while NMDA receptor activation produced NO in discontinuous areas of this layer. Thus, distinct glutamate receptors, including non-NMDA receptors, govern occurrence and level of NO production in a layer-specific manner.

Anesthetics, Local↗
PubMed1977

Functional linkage between the electrical activity in the vermal cerebellar cortex and saccadic eye movements.

The temporal relation between the onset of electrical activity of Purkinje cells and the occurrence of rapid eye movements was studied. Experiments were performed in unanesthetized animals, the recordings being made under direct vision through the use of a chronically implanted teflon sleeve. The following results were obtained. 1. Correlation between the activity of Purkinje cells and eye movements indicates that Purkinje cell firing in vermal lobules VI and VII precedes eye movement by 11-12 msec, peak activity corresponding to the time of onset of eye movement. 2. This eye movement related activity of Purkinje cells occurred regardless of the direction of the eye movements but some cells showed directional biases. Best correlation between eye movement and Purkinje cell activity was found with fast eye movements toward the right regardless of recording side. 3. Electrical activity of Purkinje cells was mainly related to saccades. Slow eye movement modulation, although probably present, was not studied in detail. 4. In those cells where an extensive set of measurements could be made, Purkinje cell firing was found to be inversely proportional to the amplitude of the eye movement, small movements being preceded by highest Purkinje cell activity. The present results suggest that cerebellar vermis responds prior to the generation of eye movement and may probably serve to control eye movements in a ballistic manner.

Animals↗
PubMed2000

Neuron loss in cerebellar cortex of rats exposed to mercury vapor: a stereological study.

Mercury vapor produces tremor in humans and experimental animals. We have previously reported that mercury vapor intoxication over an 8-week period induces only subtle changes in dorsal root ganglia and nerve roots in rats. In the present study we have carried out stereological analyses of the cerebellum of the same rats, and demonstrated significant losses of Purkinje cells (12.7%, 2P = 0.005) and granule cells (15.6%, 2P = 0.016). All sizes of Purkinje cells were lost with an equal probability, i.e. there were no indication of any preferential loss of any subpopulation of the neurons. The volume of the granular cell layer was significantly reduced (18.9%, 2P = 0.0 15), whereas the volumes of the molecular layer and the white matter were unchanged. Previous stereological studies have demonstrated that methyl mercury intoxication primarily induces degeneration in the peripheral nervous system, while sparing the cerebellum. We therefore suggest that metallic mercury vapor and methyl mercury have different toxicological profiles in rats, where metallic mercury vapor mainly affects the central nervous system and methyl mercury mainly affects the peripheral nervous system.

Animals↗
PubMed1999

Abnormal expression of tyrosine hydroxylase immunoreactivity in cerebellar cortex of ataxic mutant mice.

Expression of tyrosine hydroxylase (TH) was examined immunohistochemically in the cerebellum of two ataxic mutants, Rolling mouse Nagoya (RMN) and dilute-lethal mice (DL). In littermate controls of both mutants, a few TH-positive Purkinje cells were distributed sparsely and their number was smaller than in the mutants at any ages examined. In RMN, TH-positive Purkinje cells were distributed in lobule IX and X, and were arranged into parasagittal bands at 2 weeks of age. TH-positive Purkinje cells increased in number and were widely distributed throughout the vermis at 3 weeks of age. In adult RMN, TH-positive Purkinje cells were found in all lobules of the cerebellum. Their parasagittal bands also became evident in the hemisphere. In DL, TH-positive Purkinje cells were mainly distributed in vermal lobules IX and X, and the flocculus at 3 weeks of age. They were also found as bands in lobules IX and X. The results suggest that abnormal expression of TH in Purkinje cells may not be specific to the allelic group. Since TH promoter is activated by Ca2+, TH expression in the mutant Purkinje cells may predict neuronal dysfunction caused by alterations in cellular Ca2+ currents.

Animals↗
PubMed1996

Motor-skill learning: changes in synaptic organization of the rat cerebellar cortex.

Rats trained on motor-skill learning tasks for 30 days were previously found to have more synapses in the volume of tissue proportional to a Purkinje cell than rats that exercised or were inactive. In the motor learning tasks, hooded rats were required to traverse an obstacle course requiring balance and coordination. Rats in two exercise groups were required to walk rapidly or allowed to run in activity wheels. Controls were relatively inactive in standard housing and handled once daily. Synapses were classified to determine which synaptic types changed in number across levels of the molecular layer in the paramedian lobule. The motor learning group had significantly more parallel fiber synapses and climbing fiber synapses per unit Purkinje cell reference volume than all other groups. There were also more synapses and more parallel fiber synapses per reference volume in the outermost than in the innermost molecular layer. The plasticity reported here occurs in vivo under normal physiological conditions. Excitatory synapses account for at least 80% of the synapses in the molecular layer. The results support prior predictions that parallel fiber synapses are modifiable during conditions of learning.

Animals↗
PubMed1995

Spatial periodicity of NADPH-diaphorase and synaptophysin, but not SNAP-25, reactivity in the monkey cerebellar cortex.

We recently described a parasagittal patchy organisation of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the granular layer of the rat cerebellum. We now report the pattern of NADPH-d distribution in the primate cerebellum and its relationship to two synaptic proteins, synaptophysin and synaptosomal associated protein 25 kDa (SNAP-25), using histochemistry and immunocytochemistry. NADPH-d reactivity was localised in the molecular and granular layers (ML, GL) and a subset of infraganglionic plexuses (IGPs), but not in the Purkinje cell layer and the white matter. In ML, the histochemical reactivity was dense and relatively homogeneous in the neuropil, and moderate in the stellate cells. A patchy organisation of NADPH-d in GL was detected in both horizontal and parasagittal sections. In the IGPs staining for NADPH-d revealed modular positive zones alternating with negative ones. The positive and negative IGP zones were usually congruent with the high and low NADPH-d reactivity in GL, respectively. Both synaptic proteins were strongly expressed in the neuropil in ML and GL, and their patterns were relatively homogeneous. However, synaptophysin was present in a subpopulation of IGPs organised in modules which corresponded to those expressing NADPH-d. Our results indicate that the NADPH-d modular system is more complicated in the primate cerebellum than in the rat. In addition, we have provided suggestive evidence of a co-expression of NADPH-d and synaptophysin in selected IGP modules in primate cerebellum, which suggests that nitric oxide may be involved in the activity of the Purkinje cells by affecting the basket cell synaptic input.

Animals↗